CH 643 060 discloses a known device for determining the diameter of a linear body, such as yarn, in which the yarn to be measured moves across the area between a radiation source and an optical detector, in which the yarn diameter is determined by the width of the shadowed part of the detector, i.e. by the number of the shadowed radiation-sensitive elements. Nevertheless, this technical solution does not deal with the problem of the stability of the light source, nor does it allow a more detailed analysis of the surface structure of yarn.
The disadvantages of the solution according to CH 643 060 are eliminated by a method for detecting the thickness of a moving linear textile formation according to EP1051595B1 (CZ 286 113), in which the linear textile formation moves in a radiation flux between a radiation source and a CCD radiation sensor, which monitors the shadow of the moving linear textile material by evaluating the degree of irradiation of the individual elements of the CCD sensor. On the basis of the shadowed elements, the actual thickness of the linear textile formation is determined. The irradiation intensity of at least one irradiated element of the CCD sensor is continuously evaluated and the intensity of the radiation emitted by the radiation source depends on comparing the intensity of the irradiation of one chosen element of the CCD sensor with a predetermined value of irradiation, by which means the desired constant intensity of the irradiation of the elements of the CCD sensor is maintained during the operation.
A more accurate method for determination of the actual thickness of a moving linear formation according to this solution is achieved by monitoring and evaluating the intensity of irradiation of the elements of the CCD sensor on the delimitation lines of the image of the moving linear textile formation.
In order to determine the thickness and homogeneity of a moving linear textile formation according to this solution, the intensity of irradiation of the elements inside the delimitation lines of the image of the moving linear textile formation is monitored and evaluated.
The device for carrying out the method according to EP1051595B1 (CZ 286 113) was further improved, especially for the purpose of achieving better and more effective evaluation of a signal of a linear optical sensor and obtaining the most accurate data possible about the yarn diameter.
Obtaining the most accurate possible data on the yarn diameter is the object of other solutions, too. For example, the U.S. Pat. No. 6,242,755 B1 discloses a method for the contactless measuring of fibrous textile material of indeterminate length, in which the textile material is irradiated within a measuring range of at least one radiation source and its shadow is projected by the radiation onto the receiving device comprising a row of sensor cells arranged next to one another. The diameter of the fibrous textile material is determined on the basis of the shadowed sensor cells and one or two neighbouring sensor cells shadowed partially, whereby the value of the cells shadowed only partially by the image of the textile material is determined proportionally in a pro rata manner to the amount of fully shadowed images.
The drawback of this solution is the difficult and complicated evaluation of partially shadowed cells on the spinning machines operating online, which is caused by the oscillations or vibrations of the fibrous textile material in front of the row of sensor cells. An individual cell may also be shadowed partially as a result of the movement of yarn during the sensing (integrating) time interval and not as a result of an actual change in the yarn diameter.
It follows from what has been mentioned above that EP1051595B1 (CZ 286 113) and U.S. Pat. No. 6,242,755B1 provide a very similar method for determining the diameter of a linear textile formation, such as yarn. This is caused by the fact that EP1265051B1 has a priority date of Jan. 14, 1998 and was not published until Oct. 13, 1999 (as CZ 286 113) and Jul. 22, 1999 (EP1051595B1 as WO99/036746)), whereas the U.S. Pat. No. 6,242,755B1 has a priority date of Jul. 8, 1999, therefore patents EP1051595B1 (CZ 286 113) having an earlier priority date were published only after the priority date of U.S. Pat. No. 6,242,755B1 and do not constitute its background art.
The disadvantage of both solutions is the fact that only a minimal length of the overall length of the measured yarn is actually measured, whereby the values measured on very short sections of the length, for example when measuring yarn thickness, it is necessary to integrate in a complicated manner before the processing itself in order to eliminate or at least minimize the influence of accidental phenomena arising during measuring very short sections of yarn and at the same to achieve the required precision of measuring the yarn parameters. This is caused by the fact that the yarn moves in front of the sensor at a certain speed, e.g. at 1 m/s, whereby the common speed of monitoring yarn using CCD optical sensors is approximately 1×1 ms. Since the radiation-sensitive elements of the CCD optical sensors used for the contactless measuring of yarn have dimensions approximately 10 μm×10 μm, such a device can achieve at a speed of motion, such as 1 m/s, the actual measuring of yarn parameters only on 1% of its overall length, which has proved to be insufficient.
Therefore a device for the contactless measuring of yarn, capable of measuring a larger part of the overall length of yarn was developed and described in CZ 298929, whose principle consists in that the radiation-sensitive elements of the optical detector are rectangular-shaped and their dimensions in the direction of the movement of yarn are greater than their dimensions in a direction perpendicular to the direction of the movement of yarn, whereby the described dimension of the sensing elements in the direction of the movement of the yarn is in the range between 15 μm to 200 μm. This means that using the same speed of the movement of yarn and the same frequency of sensing, as is stated in the preceding paragraph, it is actually possible to measure the yarn parameters in the range from 1.5% to 20% of its overall length. The radiation sensor can be composed of a CMOS optical sensor or a CCD sensor. Each of the radiation-sensitive elements of the radiation sensor arranged in a row is coupled with an evaluation device of the state and/or intensity of their irradiation, whereby the evaluation device can be an integrated part of the radiation sensor. The disadvantage of this device is especially meeting high demands for data transmission between the sensor and the processor, which results in higher requirements on the connected processor and, on the whole, it decreases the evaluation potential of the device.
The shortcomings of CZ 298929 were eliminated by a device for the contactless measuring of the properties of moving yarn according to CZ 299684, in which a linear optical sensor is incorporated on one semiconductor application specific integrated circuit (ASIC) together with at least a part of electronic circuits for processing and/or evaluation of a signal of the linear optical sensor, whereby the electronic circuits for processing and/or evaluation of a signal of the linear optical sensor are arranged along with the linear optical sensor on a common semiconductor support and/or arranged in one common case.
The advantage of such an arrangement is especially the fact that the initial operations of processing and/or evaluation of a signal of the sensor take place in one integrated circuit, and so they are not limited by the possibilities of the data flow between the sensor and the processor, since from the outlet of the device it is not necessary to transmit detailed information about which pixel is irradiated and which is not, but the data on the yarn diameter is transmitted directly in the digital form, whereby the data on the yarn diameter has substantially lower demands for data transmission, because for 1000 pixels, for example, it is not necessary to transmit 1000 bits of information, but only 10 bits of information about the width of yarn, or about the number of continuously shadowed and/or irradiated pixels. The circuits for processing and/or evaluation of a signal integrated with the sensor are able to use the same frequency as the sensor, which nowadays usually amounts to 20-40 MHz in the case of CMOS linear optical sensors.
The drawback of this solution is a purely digital evaluation system of individual pixels, when, according to the set comparison level, pixels are divided into irradiated and non-irradiated, the yarn diameter being determined by the sum of the width of the radiated pixels. In addition, it is difficult to monitor possible dusting on the pixels or on the radiation source, as well as their aging process.
EP 1015873 B1 describes a device for recording at least one parameter of a linear body which moves longitudinally, through an optical detector which is made up of two separate sensors, at least one of them being digital and at least one being analog. The detector thus comprises two types of sensors that work according to different principles or whose signals are evaluated according to different principles, one of the principles being digital and the other analog.
The advantages of this solution consist especially in the fact that apart from the diameter of a relatively smooth body, also the surface structure of the monitored body can be measured within certain limits. In the case of yarn it is, for example, possible to measure digitally the body of yarn without protruding fibers, and in the analog manner the hairiness of yarn, i.e. the percentage of fiber ends sticking out of the yarn. With the aid of the evaluation technology, this detector can be even adapted to the changed conditions of measuring and compensate for or take into account, for example, the influence of impurities and residues on the sensors. The optical detector, however, cannot be adapted to changes in external radiation and/or aging of the light source.
The disadvantage of this solution is particularly the fact that two types of different sensors are used, i.e. digital and analog, whereby signals from both types of sensors are received and recorded completely separately, and in this form they are transmitted to a superior evaluation device to be processed, which, especially in the case of the analog channel, results in the necessity of subsequent digitalization of the data obtained in this manner and their primary processing as late as in the evaluation device. This places unacceptably high demands on the computing capacity of the evaluation device, especially during on-line processing of the data on spun-out yarn which takes place directly on the production machine. Furthermore, the necessity of the correlation of the signals from the digital and analog sections of the sensor is also demanding as to the computing capacity, if it is carried out by purely programming means, as is described in the patent application. Moreover, uncontrollable movements of the yarn in a direction perpendicular to its basic production movement may unfavourably influence the analog signal obtained from the analog sensor or sensors. Apparently, this arrangement is acceptable when used in a laboratory measuring device, where the quality of yarn is evaluated off-line at a suitable speed and with proper stabilization of the position of yarn in front of a sensor, but using sensors online directly on spinning or weft-winding machines is thoroughly unsuitable both from the technical and from the economic point of view.
Another disadvantage of this device following from entirely independent processing of the signals from the digital and analog sections is the fact that each of these channels exhibits different types of errors which are dependent, for example, on the temperature or ambient light and, in the case of an analog channel, they are dependent also on noise and electromagnetic disturbing signals induced into the analog conductor which on the basis of the principle described in the patent must have a certain minimal length within which it is exposed to the influence of electromagnetic disturbance from the surrounding devices of the spinning machine.
Disturbance-free environment can be evidently created in the case of a measuring device used in a laboratory, but not when used on-line on a spinning or weft-winding machine.
Apart from the above-mentioned method for detecting thickness by a linear CCD sensor, EP1051595B1 (CZ 286 113) also describes a method for continuous monitoring of a moving linear textile formation, in which the moving linear textile formation is monitored in a plurality of planes of sensing, since the linear textile formation moves between a flat radiation source and a matrix CCD sensor, and so it should be able to be used on-line on a textile machine. The evaluation of the state and/or intensity of irradiation, however is carried out in each of the elements of the matrix CCD sensor in individual lines. The evaluation is therefore complicated, slow, and expensive, and so the device cannot be used on textile machines producing or processing yarn, such as spinning or weft-winding machines.